Click for Abeking Click for Nordhavn Click for Cross Click for Burger Click for Ocean Alexander

zinc anodes - factors affecting speed of sacrification

Discussion in 'Technical Discussion' started by balboa, Oct 6, 2007.

  1. balboa, Oct 6, 2007
    #1
    balboa

    balboa Guest

    Can anybody tell me which factors affect the speed in which zinc anodes are sacrificed?

    I assume it has to do with the conductivity of the seawater? If so, which factors affect that conductivity and are their other factors?


    Thorwald
  2. C4ENG, Oct 6, 2007
    #2
    C4ENG

    C4ENG Senior Member

    Joined:
    May 19, 2006
    Messages:
    581
    Location:
    Ft Lauderdale
    More to do with the amount of dis-similar metals in the sea water on the vessel
  3. Northern Lights, Oct 7, 2007
    #3
    Northern Lights

    Northern Lights New Member

    Joined:
    Sep 25, 2005
    Messages:
    29
    Location:
    San Diego
    zinc burn rates

    Load and or demand to do work. One can reference exacted engineering to design a sacrificial anode sytem that the anodes burn at a predicted rate. The specific ratio of anode to metals that are being protected can be measured and from this one can design a system that protects the underwater metals from haul out to haul out. The ratio can change by many factors such as coatings failure and natural wear on the coating system. Failure of the hulls coatings expose metal that increases the demand on the zincs to do work. In a perfect world you would coat the metals so perfectly that there would be little or no demand on the zincs to do work. This never is the case. The installation of diver serviceable zincs allows for a variable. If you put to many zincs on a hull the demand is so low that the zincs often stop working as they create a coating. The coating (passivication) inhibits the the zinc from working. U.S. Mil-spec zincs contain a small percentage of cabnium to avert this. With the cabnium the zincs have a burn rate regardless of the demand. The electroguard zinc uses a dolphin with a gas mask on as there logo. Electroguard zinc contain no cabnium. Enviromentist agencies say that cabnium is not good in the food life chain.
    The boat yard can usually advise you based on expierence how many zincs to use. The most important link to your underwater metals is a underwater hull cleaning service that advises you monthly. Even with a new hull painting it is important to keep an eye on the metals below the waterline.
  4. balboa, Oct 7, 2007
    #4
    balboa

    balboa Guest

    zinc anodes - impressed current cathodic protection

    Great feedback!

    Thanks a lot.

    So, would you say a ICCP system worth considering? Probably higher initial cost but down the line, it offers more secure protection it seems.

    Does it have any other drawbacks?

    Thorwald
  5. Highlander, Nov 16, 2007
    #5
    Highlander

    Highlander New Member

    Joined:
    Sep 27, 2007
    Messages:
    75
    Location:
    Milford CT
    ICCP and zincs

    The great thing about the ICCP system is continous monitoring.

    My boat has zincs too and over 8 seasons the system has alerted me to a few problems.
    Stray currents from other boats/docks.
    High rate of wear on the zincs.
    One year the yard painted over the titainium pad with bottom paint.

    In all cases the unit showed either over / under protected.
    Its a lot easyer than diving